ionisation energy

Question 1

first ionisation energy

Answer 1

the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 2

first ionisation of chlorine

Answer 2

Cl(g) —-> Cl+(g) +e-

Question 3

first ionisation of aluminium

Answer 3

Al(g) —-> Al+(g) +e-

Question 4

factors effecting ionisation energy

Answer 4

nuclear charge
distance of the outermost electron from the nucleus
electron shielding

Question 5

nuclear charge

Answer 5

more protons in nucleus greater the nuclear charge. Greater the nuclear charge the stronger the nuclear attraction on the the outer electrons. Greater nuclear charge means more energy would be needed to overcome the attraction between the nucleus and the outermost electron

Question 6

distance of the outermost electron from the nucleus

Answer 6

as the distance between the nucleus and the outermost electron increases the attraction between them decreases. The weaker the nuclear attraction the less energy is needed to remove the outer electron

Question 7

electron shielding

Answer 7

repulsion between electrons from the inner shells and the outer shell electron. This shielding effect reduces the net nuclear attraction from the positive nucleus on the outer shell electron. The more inner shells there are the greater the shielding effect and the weaker the nuclear attraction experienced by the outer electrons meaning a lower ionisation energy

Question 8

general trend down a group

Answer 8

first ionisation energy decreases down a group
there are more shells
more electron shielding from inner shell electrons
the atomic radius increases the increased electron shielding and increased atomic radius far outweigh the increase in nuclear charge
nuclear attraction on outer shell electron decreases
less energy is needed to remove the outer electron

Question 9

general trend across a period

Answer 9

first ionisation energy shows a general increase across a period
the outer electrons fill the same shell so electron shielding stays the same
number of protons increases so nuclear charge increases
atomic radius decreases
greater nuclear attraction on the outer electrons
more energy needed to remove the outer electron

Question 10

why does boron have a lower first ionisation energy than beryilium

Answer 10

2p subshell in B has a higher energy than the 2s subshell in Be
2p1 electron in B needs less energy to be removed giving B a lower first ionisation energy than Be

Question 11

why does oxygen have a lower first ionisation energy than nitrogen

Answer 11

due to electron pairing in the p orbital O
in N each p orbital contains 1 unpaired electron
In O one p orbital now contains 2 electrons paired
The paired 2p electrons in oxygen repel each other meaning it is easier to remove one of these electrons
So less energy is needed to remove the 2p electron from O than from N

Question 12

fourth ionisation of copper

Answer 12

Cu+3(g) —-> Cu+4(g) +e-

Question 13

seventh ionisation of bromine

Answer 13

Br+6(g) —-> Br+7(g) +e-

Question 14

how many ionisation energies are possible for boron

Answer 14

5 as boron has 5 electrons

Question 15

successive ionisation energies

Answer 15

a measure of the energy required to remove each electron in turn

Question 16

explain why successive ionisation energies always increase with ionisation number

Answer 16

each time an electron is removed
the proton to electron ratio increases (same number of protons attract fewer electrons)
there is a greater nuclear attraction on the remaining electrons